Hi,

The origin of the non-standard time zone known as Amsterdam Time has a long and interesting history but to save you the trouble of wading through the website mentioned in earlier postings, the following will probably suffice.

The adopted value of 0h 19m 32.13s was obtained by comparing the longitude of Leiden Observatory with the central meridian of the Topographische Kaart van het Koninkrijk der Nederlanden ("Topographical Map of the Kingdom of the Netherlands") which ran exactly through the Westertoren in Amsteradm and the longitude difference between Leiden Observatory and Greenwich Observatory as listed in the <i>Nautical Almanac</i>.

Details can be found in this paper

  Hk. J. Heuvelink, "Amsterdamsche tijd", <i>De Ingenieur</i>, vol. 23 (1908), pp. 895-896,

 online here https://resolver.kb.nl/resolve?urn=dts:2951065:mpeg21:pdf

See also p. 301 of

https://ui.adsabs.harvard.edu/abs/1909Obs....32..297./abstract

rvg

From: tz <tz-bounces@iana.org> On Behalf Of Eitan Adler via tz
Sent: Tuesday, August 6, 2024 12:19 AM
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: Time zone mailing list <tz@iana.org>
Subject: Re: [tz] netherland timezone UTC offset (0:19:32.13) history

CAUTION: This email originated from outside of Utrecht University. Do not click links or open attachments unless you recognize the sender and know the content is safe.

On Mon, 5 Aug 2024 at 09:53, Paul Eggert <eggert@cs.ucla.edu> wrote:
>
> On 2024-08-05 09:22, Tim Parenti via tz wrote:
> > That page is the responsibility of Robert Harry van Gent and is hosted
> > by the Faculty of Science at Universiteit Utrecht.
>
> Van Gent cites many sources for Amsterdam time (mostly in Dutch) here:
>
> https://webspace.science.uu.nl/~gent0113/wettijd/wt_text6b.htm
>
> Many of his sources are contemporaneous. It's an impressive list.
>
> Although it's not clear whether the ".32.13" is van Gent's calculation
> or is copied verbatim from one of those sources, it's surely close to
> the correct value insofar as that can be determined.

Wow! Thank you both.

The Van Gent site in particular certainly seems complete - though I don't speak dutch.

--
Eitan Adler